Rotatable charged particle beam deflector



Jan. 18, 1966 s. R. FARRELL ROTATABLE CHARGED PARTICLE BEAM DEFLEGTORFiled Jan. 3, 1962 United States Patent 3,230,409 ROTATA-BLE CHARGEDPARTICLE BEAM DEFLECTOR Sherman R. Farrell, Orinda, Califl, assignor, bymesne assignments, to High Voltage Engineering Corporation,

Burlington, Mass., a corporation of Massachusetts Filed Jan. 3, 1962,Ser. No. 164,120 7 Claims. (Cl. 31360) This invention relates toparticle accelerators and apparatus for deflecting charged particlebeams generated thereby. More particularly, it discloses a rotatablebeam deflector that, through a novel combination and arrangement ofbellows, bellows restraining means, and magnetic field producing means,provides 360 rotation of the deflected beam.

It is often desirable to utilize the beam generated by a particleaccelerator in some direction other than that of its projected axis.This is especially true in the production of X-rays wherein spaceeconomies dictate that inherently long particle accelerating devicessuch as linear accelerators and Van de Graaff generators be disposed ina particular fixed position. Most commonly a 90 deflection of theprojected beam is required. Further system flexibility is achieved bymaking the beam thus deflected rotatable about its original -projectedaxis. Complete 360 rotation is most desirable, and in many instancesrequired. A review of the current state of the art reveals thatheretofore attempts to develop such a system have been predicated on theuse of magnetic beam bending means in combination with a rotating vacuumjoint. It

"is well known, however, that rotating vacuum joints are generallyunsatisfactory and are replete with vexatious maintenance problems.Also, the rigid vacuum requirements of high power particle acceleratorsfurther dictate against the use therein of such a device.

Accordingly, it is a principal object of my invention to provide a newand improved rotatable charged particle beam deflector.

It is a further object of my invention to provide beam deflectingapparatus of the type described whereby 360 rotation of the deflectedbeam is achieved without resort to a rotating vacuum joint.

It is a still further object of my invention to provide a rotatablecharged particle beam deflector wherein rotation of the deflected beamis achieved by means of a flexible metal bellows.

Another object of my invention is to provide, for use in conjunctionwith an electron linear accelerator, apparatus adapted to direct thebeam generated thereby at right angles to the longitudinal axis thereoffor the purpose of high density X-ray production where limited space isa controlling factor.

These, together with other objects and advantages will become apparentfrom the following detailed description of one presently preferredembodiment of my invention. While my invention is described withreference to specific structure, it is not intended that it be limitedthereto, the full scope and nature thereof being defined in the appendedclaims.

In the accompanying drawings wherein like numerals refer to like partsthroughout;

FIGURE 1 is a front view of one presently preferred embodiment of myinvention;

FIGURE 2 is a sectional View of FIGURE 1 taken at 22; and

FIGURE 3 illustrates a second alternate embodiment of my invention.

Referring now to FIGURES 1 and 2, there is illustrated a rotatablecharged particle deflector of the 'type comprehended by my invention. Inoperation, a charged particle 3,230,409 Patented Jan. 18, 1966 ice beamis generated in, and projected along the axis of, linear accelerator 3.The expression linear accelerator as used herein is intended to beconstrued in its broadest sense, including Van de Graaff generators,Cockcroft Walton accelerating tubes and the like. Flexible bellows 6,preferably of non-magnetic metal such as copper, is attached to theoutput end of linear accelerator 3. The junction therebetween is made bymeans of vacuum seal 10 thereby extending the vacuum system throughbellows 6. The end of bellows 6 is provided with collar 14 to allow theattachment thereto of X-ray target 7. Vacuum seal 11 insures maintenanceof the desired vacuum. Bellows restraining means 4, in the presentillustrative embodiment, comprises a tubular right angle elbow member ofnon-magnetic material such as copper. The inner diameter of said bellowsrestraining means is roughly equal to the inner diameter of linearaccelerator 3 and is in slideably contiguous relationship with bellows 6therein disposed. The housing of linear accelerator 3 has disposed onthe output end thereof annular collar 8, said collar 8 being operablyengaged with annular groove 9 of bellows restraining means 4. Such anengaging relationship, then, allows bellows restraining means 4 torotate freely around the longitudinal axis of linear accelerator 3. Theend extremity of bellows restraining means 4 is provided with bearing'means 12 disposed on the inner circumference thereof. Said bearingmeans 12 insures unrestricted precession of the out-put end of bellows 6during deflector rotation. A uniform magnetic field is provided bymagnets 5 thereby deflecting the charged particle beam passingtherebetween the desired amount.

Referring now to the alternate embodiment of my invention illustrated inFIGURE 3, it is seen that for deflectors whose excess weight precludesthe cantilever arrangement hereinbefore described, a mounting platform16 may be provided upon which magnets 5, bearing 12, and bellowsrestraining means '15 maybe mounted. The platform 16, in such anarrangement is maintained a fixed distance from the end of linearaccelerator 3 and is made to rotate about the longitudinal axis thereof.In this embodiment it is only necessary to provide an arcuate sector 15for the bellows restraining means. A concave arcuate surface 17 issuflicient to maintain bellows 6 in the correct position.

There has thus been disclosed novel apparatus whereby the severalobjects of my invention are accomplished. It is not intended that theinvention thus disclosed be limited by the particular apparatusdescribed since various modifications and applications within the spiritand scope thereof will occur to those skilled in the art. For instance,it is apparent that operation at various angles of deflection may bereadily obtained and that various applications other than the productionof X-ray beams may be utilized. Furthermore automatic rotating means anddemountable, exchangeable units may be employed without departing fromthe scope of my invention. Therefore although specific apparatus hasbeen described in setting forth my invention, it is not to be taken byway of limitation, the extent of my invention being defined in theappended claims.

I claim:

1. In a particle accelerator, a rotatable beam deflector comprising anevacuated flexible member having one end thereof in fixed relationshipto the output end of said accelerator, said flexible member beingpositioned to admit the passage of the particle beam therethrough, meansadapted to bend said flexible member and rotate the unsecured endthereof, and means adapted to bend said particle beam to conform to saidflexible member.

2. A rotatable beam deflector as defined in claim 1 wherein saidevacuated flexible member comprises an electrically conductive metalbellows.

3. A rotatable beam deflector as defined in claim 1 wherein said meansadapted to bend said flexible member and rotate the unsecured endthereof comprises in combination, a platform means, said platform meansbeing positioned a discrete distance from the output end of saidaccelerator normal to and rotatable about the longitudinal axis thereof,flexible member restraining means mounted thereon, said restrainingmeans being contiguous to and arranged to constrain said flexible memberin an arcuate configuration, and bearing means, said bearing means beingmounted on said platform and adapted to rotate the unsecured end of saidflexible member about the longitudinal axis of said accelerator withoutrestricting the precession of said flexible member about its own axis.

4. A rotatable beam deflector as defined in claim 1 wherein said meansadapted to bend said particle beam to conform to said flexible membercomprises permanent magnet means disposed to provide a uniform magnetfield in transverse relationship to said flexible member.

5. In a particle accelerator adapted to generate a high energy chargedparticle beam, a rotatable beam deflector comprising an evacuatedflexible metal bellows having one end thereof fixedly attached to theoutput end of said accelerator, said bellows being aligned therewith toallow the passage of said charged particle beam therethrough, meansadapted to bend said flexible member a bellows restraining memberadapted to direct and rotate the output end of said bellows, saidrestraining member being in slideable relationship to said bellows toallow precession of the output end thereof, and means for providing auniform magnetic field adapted to direct said charged particle beamthrough said bellows.

6. In a particle accelerator for generating a high energy electron beamalong the longitudinal axis thereof, apparatus adapted to provide 90deflection and 360 rotation of the electron beam projected therebycomprising a flexible electrically conductive metal bellows attached tothe output end of said accelerator and arranged to provided an extensionof the vacuum system thereof, a bellows restraining member, saidrestraining member being rotatably affixed to the output end of saidaccelerator and operably engaged with said bellows to provide a 90 bendtherein and to impart rotation thereof about the longitudinal axis ofthe linear accelerator, the output end of said bellows being free toprecess on its own axis during said rotation, and means for providing auniform magnetic field in transverse relationship with said bellowsadapted to confine the electron beam therein.

7. In combination with a particle accelerator adapted to project a highenergy electron beam along the longitudinal axis thereof, apparatus forbending said beam 90 and rotating said bent portion thereof around thelongitudinal axis of said accelerator comprising a flexible electricallyconductive metal bellows, one end of said bellows conforming with theoutput section of said linear accelerator and being aflixed theretothrough a vacuum tight seal, an X-ray target, said X-ray targetproviding a vacuum-tight closure to the end aperture of said bellows,bellows restraining means, said bellows restraining means comprising anelectrically conductive tubular metal elbow member rotatably connectedto the output end of said linear accelerator, said bellows beingdisposed therein and constrained thereby to form a 90 angle with thelongitudinal axis of said linear accelerator, and permanent magnetmeans, said permanent magnet means being affixed to said bellowsrestraining means and adapted to provide a uniform magnetic field intransverse relationship to said bellows.

References Cited by the Examiner UNITED STATES PATENTS 2,209,963 8/1940Du Mond a- 313 X 2,421,086 5/1947 Sabol 3 13-149 X 2,429,558 10/1947Marton 3l7200 X 2,626,359 1/1953 Weber 3 1385 X 2,737,593 3/1956Robinson 313- X 2,837,656 6/1958 Hendee et al. 25051.5 2,866,113 12/1958Cosslett 313--57 2,922,904 1/1960 Zunick 313-57 X 2,959,700 11/1960Campanile 313-148 X GEORGE N. WESTBY, Primary Examiner.

ARTHUR GAUSS, Examiner.

1. IN A PARTICLE ACCELERATOR, A ROTATABLE BEAM DEFLECTOR COMPRISING ANEVACUATED FLEXIBLE MEMBER HAVING ONE END THEREOF IN FIXED RELATIONSHIPTO THE OUTPUT END OF SAID ACCELERATOR, SAID FLEXIBLE MEMBER BEINGPOSITIONED TO ADMEIT THE PASSAGE OF THE PARTICLE BEAM THERETHROUGH,MEANS ADAPTED TO BEND SAID FLEXIBLE MEMBER AND ROTATE THE UN SECURED ENDTHEREOF, AND MEANS ADAPTED TO BEND SAID PARTICLE BEAM TO CONFORM TO SAIDFLEXIBLE MEMBER.